Extreme Advanced Dive. See my map ( http://scubaonthe.net/lanai.html ) for detailed info. Bring flashlight, someone to watch the car for break-ins & make sure you get back, & a local guide. Leave all valuables at home, & put a sign in the window: "no cash, no radio." From Waikiki, drive past Diamond Head. At Port Lock before Hanauma, find a dive shop with a local guide. Then drive past Hanauma toward Blowhole. Lanai's the 1 parking lot between Hanauma & Blowhole: a square for 20 cars, on a barren rocky triangular point. No phones, bathrooms, park staff-- have your car-watcher bring a cell phone. Don gear, keep wetsuit unzipped, clip your fins in top clip of BCD, do a sincere willingness check, & shove your mask into the foot-pocket of a fin. Along the highway, walk away from Hanauma Bay/Waikiki & cross the road to the inshore side of the road. When you see a small valley, walk down into it & you will find a dark narrow stone tunnel under the road. If you have a flashlight, now's the time to use it; the tunnel floor has ankle-twister holes in it. & After the tunnel, there is a tiny climb down a 3' ledge, onto a slippery flat rocky point. Beware of slipping here; there's lots of moss. Best to have pressed-felt reef boots (called "tabi" in Hawaii & Japan) to grip the ground here. Let the guide show you where to enter. DO NOT go near the innermost bays; they're extreme hazards. Giant-stride entry, sink immediately. The surface is unsafe: waves, whitewater, sharp rocks. Divers meet on bottom, 30' down. Send your 2nd-best diver to the bottom first; keep your first-best at the surface 'til last, to assist divers entering the water. You'll see a 30'-wide, 10'-tall tunnel immediately below entry point. Go through; head toward the parking lot. Cut across the narrow, boulder-strewn bay beyond the tunnel, & find a wall, outer edge of the rocky point where you parked. Follow the wall, any depth >15';. Beware, the top of the wall is extremely surge-ridden whitewater, a shallow shelf covered in waves. That shelf's edge is a great place to spot humpback cowries, though. Follow the wall for 30 minutes, until a salt-and-pepper sandy plain with wave-ridges, 30' deep. This is the last safe playground/place-to-surface before the exit, & this is where your friendly guide earns his/her $. The exit area is whitewater & surge-ridden. Worse, there're misleading false exits on either side of the real. Look for a small overhang in 15' of water, with piercings in the side & front that prevent it from being a true cavern. The near side of it is a false exit; its far side is true. Better, if you have the air & a truly knowledgeable guide, he/she will lead you past the exit to the "cheesegrate" cove beyond it, where a black 30' tunnel will lead you unerringly into the middle of the true exit cove, which is J-shaped, 40' long, & sloped upward from 10' to 1'. Use its rocky bottom as handholds & let the surge bring you in. As you 'round the J, you will be brought into a hottub-like area where you can safely exit. DO NOT PAUSE at the hottub; clamber out quickly. Waves rip over the rocks & can push you back into the bottom of the J, or pull you out over the rocks into the open sea. Get ready for a steep, dry, dusty, slippery walk up to the parking lot. Iffy divers, try out & back from the exit cove to gain familiarity. Experienced Lanai Lookout divers good on air may want to enjoy "windchime canyon" past the cheese grate cove, or even try drift-diving from exit cove to Hanauma Bay's "Toilet Bowl".